Thermodynamic apparatus for cooling and heating by adsorption on a solid adsorbent and process for using the same

ABSTRACT

The invention relates to an improved thermodynamic apparatus for cooling or heating by adsorption of a refrigerating fluid on a solid adsorbent. The apparatus includes--a hot circuit adapted to heat and circulate a heating fluid;--a cold circuit adapted to cool and circulate a cooling fluid;--a cooling circuit for an enclosure to be air-conditioned;--two tanks containing a solid compound with large capacities but having a low energy of adsorption, said tanks, connected together and to the different. The two tanks comprising: at least one reactor adapted to receive said adsorbent compound, at least one condenser adapted to condense the refrigerating fluid desorbed under the effect of the action of the hot fluid passing through the adsorbent compound laden with refrigerating fluid, at least one evaporator adapted to vaporize the refrigerating fluid adsorbed on the adsorbent compound cooled by the cold circuit, such that:--the hot circuit is adapted to be connected to the reactors of the two tanks;--the cold circuit is adapted to be connected either to the condensers or to the reactors of the two tanks;--finally, the cooling circuit is adapted to be connected to the evaporators of the two tanks.

The present invention relates to an apparatus for the production of heator cold utilizing a source of heat, and by adsorption on a solidadsorbent. It relates more particularly to a novel process ofrefrigeration from a source of energy of which the temperature range isincluded between 100° and 300° C., such as in particular solar energy.It also relates to a process for implementing such an installation.

Techniques are known for producing cold from a hot source by adsorptionof a refrigerating fluid on a solid adsorbent (cf. in particular U.S.Pat. Nos. 1,881,208, 2,377,589 and 3,270,512 and British Pat. No.385,407). Briefly, such installations essentially comprise:

a hot circuit adapted to heat and circulate a heating fluid;

a cold circuit adapted to cool and circulate a cooling fluid;

a cooling or air-conditioning circuit for the enclosure to beair-conditioned;

two tanks containing a solid compound having a large capacity but a lowenergy of adsorption, these two tanks, connected together and to thedifferent circuits, comprising:

at least one exchanger, called "reactor", adapted to receive saidadsorbent compound and have this compound to react with therefrigerating fluid;

at least one condenser adapted to condense the refrigerating fluidevaporated under the effect of the action of the hot fluid passingthrough the adsorbent compound laden with refrigerating fluid,

at least one evaporator adapted to vaporize the refrigerating fluidadsorbed on the adsorbent compound cooled by the cooling fluid circuit.

In Applicants' French Patent FR-A-2 465 970, corresponding to PCT-WO81/00904 (PCT/FR 80/00139), it was suggested, before the inversion ofthe adsorption-desorption cycle, i.e. when each tank is close to itspoint of equilibrium, to equalize the temperatures between these twotanks.

However, the above-mentioned prior art solutions, present numerousadvantages, but require pipes and valves adapted to work underrefrigerating fluid pressure, i.e. in depression if these fluids arewater or methanol and under excess pressure for other fluids such asammonia, which, during the cycle, generates considerable pressure dropslikely to bring about a drop in temperature which is generally estimatedat around 10° C. for water. Furthermore, as the different valvesconnecting the pipes and the circuits together must be capable ofworking under this refrigerating fluid pressure, this creates leakages,and, substantially increases the total cost of these installations.

It is an object of the present invention to overcome these drawbacks andto this end an installation of the present invention includes twoadsorbent tanks, which do not require special pipes or valves to workunder refrigerating fluid pressure and is consequently more economicalboth to construct and operate. In addition, this installation presentsan improved COP (coefficient of performance).

This improved cooling apparatus by adsorption of a refrigerating fluidon solid adsorbent, of the present invention comprises:

a hot circuit adapted to heat and circulate a heating fluid;

a cold circuit adapted to cool and circulate a cooling fluid;

a cooling or air-conditioning circuit for the enclosure to beair-conditioned;

two tanks containing a solid compound having a large capacity but with alow energy of adsorption, said tanks, connected together and to thedifferent circuits, comprising:

at least one reactor adapted to receive said adsorbent compounds,

at least one condenser adapted to condense the refrigerating fluiddesorbed under the effect of the action of the hot fluid passing throughthe adsorbent compound laden with refrigerating fluid,

at least one evaporator adapted to vaporize the refrigerating fluidadsorbed on the adsorbent compound cooled by the cold circuit.

This installation is characterized in that:

the hot circuit is adapted to be connected to the reactors;

the cold circuit is adapted to be connected either to the condensers orto the reactors of the two tanks;

finally, the cooling circuit is adapted to be connected to theevaporators of the two tanks.

Preferably:

the tanks are composed of a horizontal, cylindrical, one-piece tankproper, under refrigerating fluid pressure, which comprises:

the reactor itself constituted by a plurality of parallel finned tubes,the space between the tubes being at least partially filled withadsorbent compound, said tubes being placed to form a circle,

at the centre, a member forming both evaporator and condenser, namelythe "evaporator-condenser", constituted either by a plurality ofsuperposed plates parallel to one another and parallel to the tubes, orby a trickling exchanger,

an anti-radiation screen disposed between the evaporator-condenser andthe finned tubes,

toric manifolds connecting the tubes and the evaporator-condenser to thedifferent inlets and outlets of the different circuits.

the source of heat of the hot circuit is constituted by a solarcollector or by a boiler;

the source of cold of the cold circuit is constituted by an air coolantor by a cooling tower, connected to the ambient air or by an availablecooling fluid circuit;

the cooling circuit comprises either an air-water battery or any otherheat exchanger, which also is capable of producing ice;

the three circuits and the two tanks are connected together byconventional pipes and valves under water or thermal oil pressure;

the solid absorbent is selected from the group including zeolites,activated charcoals, gels of silica and activated alumina; therefrigerating fluid is selected from the group including water, methanoland ammonia.

The invention also relates to a process for implementing such anapparatus.

This process comprises the following steps:

a first stage of, simultaneously, connecting:

the hot circuit to the reactor of the first tank to provide desorptionof the heating fluid thereof,

the cold circuit to the reactor of the second tank to allow adsorptionof the refrigerating fluid thereon,

and simultaneously, remaining the heat furnished by the condensation ofthe refrigerating fluid on the evaporator-condenser of the first tank bythe cold circuit and taking from the cooling circuit the energy ofvaporization of the refrigerating fluid on the evaporator-condenser ofthe second tank;

a second stage, after having connected together the reactors of the twotanks so that a thermal equilibrium between these reactors can bereached, cooling of the first tank which begins to adsorb allowspre-heating of the second tank which begins to desorb, remaining thehead furnished by the condensation of the refrigerating fluid on theevaporator-condenser of the second tank on the cold circuit and takingfrom the cooling circuit the energy of vaporization of the refrigeratingfluid on the evaporator-condenser of the first tank;

a third stage, while continuing to remove the heat furnished by thecondensation of the refrigerating fluid on the evaporator-condenser ofthe second tank on the cold circuit and to take from the cooling circuitthe energy of vaporization of the refrigerating fluid on theevaporator-condenser of the first tank, connecting:

the hot circuit to the reactor of the second tank for desorption of thelatter,

the cold circuit to the reactor of the first tank for adsorption of thelatter;

a fourth stage, after having connected the reactors of the two tankswith a view of effecting thermal equilibrium between these two reactorsagain, for the cooling of the second tank which begins to adsorb toallow pre-heating of the first tank which begins to desorb, removing theheat furnished by the condensation of refrigerating fluid on theevaporator-condenser of the first tank by the cold circuit and takingfrom the cooling circuit the energy of vaporization of the refrigeratingfluid on the evaporator-condenser of the second tank;

and finally, a fifth stage, connecting:

the hot circuit on the reactor of the first tank,

the cold circuit to the reactor of the second tank,

and continuing to remove the heat generated by the condensation of therefrigerating fluid on the evaporator-condenser of the first tank by thecold circuit and continuing to draw from the cooling circuit the energyof vaporization of the refrigerating fluid on the evaporator-condenserof the second tank.

The different connections are controlled by a regulating member whichcontrols the opening and closure of the different valves placed in thepipes of the different circuits.

Although the following embodiment refers to a cooling installation, theinvention may also be adapted for the production of heat, withoutdeparting from the scope the present invention.

The invention will be more readily understood on reading the followingdescription with reference to the accompanying drawings, in which:

FIG. 1 schematically shows an installation according to the invention.

FIGS. 2 and 3 respectively show, in section and in cross section alongaxis II--II, the one-piece tank characteristic of the invention.

FIGS. 4 to 7 schematically illustrate the principal phases of operationof the process.

Referring now to the drawings, the installation for cooling byadsorption on solid adsorbent (cf. FIG. 1) comprises:

a source of heat 1 such as a solar collector or a boiler, to heat andcirculate a heating fluid, such as water or oil, through conventionaloutlet pipe 2 and return pipe 3. The assembly 1, 2, 3 thus forms the hotcircuit;

a cold source 4 for example, a cooling tower or an air-coolant,connected to the ambient air, intended to cool and circulate a coolingfluid, such as water, through conventional outlet pipe 5 and return pipe6. The assembly 4, 5, 6 forms the cold circuit;

a cooling circuit 7, for example to air-condition, placed in theenclosure (not shown) to be air-conditioned, such as premises or a coldroom or even an ice-making chamber, with its air-water battery 8 and itsconventional outlet (9) and return (10) connecting pipes. The assembly7, 9, 10 forms the air-conditioning circuit; all the pipes 2, 3, 5, 6,9, 10 are conventional pipes under water pressure or under pressure ofother appropriate fluids: thermal oils;

two one-piece tanks, namely, a first tank 11 and a second tank 12 asshown in detail in FIGS. 2 and 3; the one-piece tanks 11, 12 beingessentially constituted by:

a bottom 40 on which open out the different outlet and return pipesmentioned hereinabove,

a horizontal tank 41 substantially cylindrical in form, for examplesmade of stainless steel, connected to the bottom 40 by flanges 51,

a plurality, for example six, of tubes 42, 43 provided with parallelradial fins 44 filled with a solid adsorbent compound 45 having a highcapacity of adsorption and a low energy of adsorption, such as forexample a zeolite of type 13 X; these tubes 42, 43 form the reactor andare placed to form a circle on the inner periphery of the tank 41, andfilled with water vapour 46 in vacuo, the space defined by outercylindrical screen 49 and the horizontal tank 41

two plates 47, 48 parallel to each other and also parallel to the tubes42, 43 form an evaporator-condenser; as has already been said, theseplates 47, 48 may be replaced by a trickling exchanger such as a bundleof finned tubes over which the refrigerating fluid trickles in closedcircuit in the tank;

two cylindrical screens 49, 50 coaxial to the tank 41 and which enclosethe plates 47, 48 therein; these two anti-radiation screens 49, 50 mayfor example be made of polished aluminium sheet, and used to inhibitheat exchange between the plates 47, 48 and the reactor tubes 42, 43,

a first toric manifold 52 connecting the different inlets of thereactors 42, 43, and a second likewise toric manifold 53 connecting theoutlets of this same reactor 42, 43,

two straight manifolds 54, 55 outside the tank 41 connecting the plates47, 48 to the different inlets or outlets of the different circuits;

a plurality of valves 20 to 31 placed in the pipes 2, 3, 5, 6, 9, 10 areessentially of two types:

either conventional simple valves 20 to 29, i.e. two-way valves, adaptedto work under water or other fluid pressure,

or conventional multiple valves 30, 31 (four-way);

a conventional regulating member 32 connected by connections 33 to thedifferent valves 20 to 31, in order to control the opening and closureof these valves.

In these Figures, reference dash (') symbolizes the second tank 11.

The installation operates as follows:

FIRST PHASE

Desorption in 12, adsorption in 11 (FIG. 4):

At the start, the hot source 1 is connected by pipes 2, 3 (circuit indotted lines) on tubes 42, 43 of the first tank 12. The heating fluidflowing from the source 1 is sent to tubes 42, 43 of the reactor.

The zeolite contained between fins 44 is thus desorbed. Consequently,the water of the zeolite condenses on plates 47, 48 of the first tank12.

The heat recovered on these plates is then removed to the cold source 4by the circuit shown in dashed lines, due to the interchange of thevalves 30, 31. Simultaneously, the cold source 4 is connected by thecircuit in dashed lines to the reactors 42' of the second tank 11. Inthis way, the zeolite contained on these tubes 42' adsorbs water vapourcoming from the evaporator-condenser plates 47', 48' of this second tank11. The necessary vaporization heat is then taken from theair-conditioning circuit 7 by the pipes 9, 10 and by the valves 30, 31(circuit shown in dashed and dotted lines), in order to cool the waterbattery 8 of this air-conditioning circuit 7.

During the whole of this first phase, the valves 21, 23, 26, 28 areopen, whilst valves 20, 22, 24, 25, 27, 29 are closed.

The four-way valves 30, 31 thus act in both directions.

SECOND PHASE

Internal exchange (FIG. 5):

When for example, with the aid of a pressure sensor 60 or temperaturesensor, the end of adsorption or of desorption in the two tanks 11, 12is detected, it is sought to recover the internal heat of these twotanks 11, 12.

To this end, by applying the teaching of Applicant's French PatentApplication FR-A-2 465 970, the reactors 42, 43, 42', 43' with zeoliteof the two tanks 11, 12 (circuits shown in dotted lines) are connectedtogether thanks to valves 20, 25. In this way, the water circulatesbetween the two tanks 11, 12 so that the cooling of the first tank 12which begins to adsorb allows pre-heating of the second tank 11 whichbegins to desorb. This improves yield.

Simultaneously, the valves 30 and 31 and opened so as to ensure:

on the one hand, the connection between the air-conditioning circuit 7and the evaporator-condenser 47, 48 of the first tank 12 (circuit indashed and dotted lines);

on the other hand, the connection between the cold circuit 4 and theevaporator-condenser 47', 48' of the second tank 11 (circuit in dashedlines).

When thermal equilibrium between the two reactors has been attained, theexchange between these two reactors is stopped by closing valves 20 and25.

THIRD PHASE

Desorption of 11-adsorption on 12 (FIG. 6):

Here, the hot source 1 is switched on the reactor 42', 43' of the secondtank 11 by opening the valves 24 and 29 (circuit in dotted lines). By aprocess similar to phase I but in the reverse direction, desorptioncontinues on the evaporator-condenser 47', 48' contained in this secondtank 11 and the heat furnished by the evaporator-condenser of this tank11 continues to be removed towards the cold course 4 (circuit in dashedlines) by opening valves 30 and 31.

Simultaneously, by opening valves 22 and 27, the cold source 4 isswitched on the reactors 42, 43 of the first tank 12 (circuit in dashedlines) which continues to adsorb in this way water vapour coming fromthe evaporator-condenser of this tank 12. The heat continues to be takenfrom the plates 47, 48 of the first tank 12 towards the air-conditioningcircuit 7 thanks to valves 30 and 31 (circuit in dashed and dottedlines).

The end of this third phase is detected, as previously.

During this phase, only valves 22, 24, 27, 29 are open, the four-wayvalves 30 and 31 acting in both directions.

FOURTH PHASE

Internal exchange (FIG. 7):

As in phase two, the internal exchange between the two tanks 11 and 12is effected. In this way the second tank 11 is cooled and begins toadsorb, while the first tank 12 is preheated and begins to desorb.

Simultaneously, valves 30 and 31 are open so as to ensure:

on the one hand, the connection between the air-conditioning circuit 7and the evaporator-condenser 47', 48' of the second tank 11 (circuit indashed and dotted lines);

on the other hand, the connection between the cold circuit 4 and theevaporator-condenser 47', 48' of the first tank 12 (circuit in dashedlines).

FIFTH PHASE

Desorption in 12-adsorption in 11 (FIG. 4):

When thermal equilibrium between the reactors of the two tanks 11 and 12is attained,

the hot circuit 1 is switched on the reactor 42, 43 of the first tank12;

the cold circuit 4 is switched on the reactor 42', 43' of the secondtank 11;

and the heat furnished by the condensation of the water on theevaporator-condenser 47, 48 of the first tank 12 continues to beevacuated by the cold circuit 4 and the energy of vaporization of therefrigerating fluid on the evaporator-condenser 47', 48' of the secondtank 11 continues to be taken from the air-conditioning circuit.

In brief, this virtually reproduces phase one, at least at the level ofthe circuits.

The cycle then recommences.

During all these phases (FIGS. 4 to 7), the movements of opening and ofclosing of the different valves are ensured by a conventional regulatingmember 32 connected by connections 33 to each valve in question.

In fact, this regulator 32 controls essentially three groups of valves,namely

valves 20 and 25 in opposition with all the other two-way valves, namely21, 22, 23, 24, 26, 27, 28, 29;

valves 21, 23, 26, 28 in opposition with valves 22, 24, 27, 29;

the four-way valves 30, 31 controlled by 32.

In FIGS. 4 to 7, the circuits in dotted lines represent the phases ofdesorption and the phases of recovery of the heat, whilst the circuitsin dashed lines represent the phases of adsorption and of condensationand finally the circuits shown in dashed and dotted lines illustrate thephases of evaporation.

The installation according to the invention presents numerous advantagesover what was known heretofore. For example:

the semi-continuous production of cold;

the absence of mobile elements in the sensitive parts, i.e. in the tanks11, 12;

the fact that it is not necessary to use special pipes or valves,particularly valves or pipes capable of working under refrigeratingfluid pressure; consequently, conventional pipes or valves may be used,simplifying the problems of tightness;

the phases of equilibrium two and four enable improved COPs to beobtained;

the possibility of using hermetic tanks due to the one-piece structure.

Consequently, these installations may be successfully used:

the air-conditioning premises from a hot source, such as for example asolar collector;

for preserving food in hot countries;

as heat pump (production of heat), by using the energy furnished inadsorption and in condensation: by recovering all the energy furnishedto the cold source, premises may thus be heated, particularly by takingfrom the ambient air the energy of vaporization;

in addition, by replacing the zeolite by activated charcoal as adsorbentbody and the water of the circuit by methanol, the production of ice orconservation at low temperature may even be envisaged.

Although the installation more advantageously comprises two tanks, itmay, however, be interesting, for certain applications, particularlywhen the hot source is at high temperature (for example of the order of250° C.), to use three tanks connected together in accordance with theteaching of the invention.

What is claimed is:
 1. An improved thermodynamic apparatus employingadsorption of a refrigerating fluid on a solid adsorbent, for cooling orheating, comprising:two interconnected tanks containing a solid compoundhaving a large capacity but a low energy of adsorption, each tankhaving:(i) at least one reactor for receiving said adsorbent compound;(ii) at least one condensor for condensing refrigerating fluid desorbedby the action of a hot fluid passing through adsorbent compound ladenwith refrigerating fluid; (iii) at least one evaporator for vaporizingrefrigerating fluid adsorbed on the adsorbent compound cooled by a coldcircuit; a hot circuit connectible to the at least one reactor of eachof the two tanks for heating and circulating said hot fluid; anair-conditioning circuit connectible to the at least one evaporator ofeach of the two tanks for cooling an enclosure to be air-conditioned;wherein said cold circuit is alternately connectible to the at least onecondensor and the at least one reactor of the two tanks; and whereineach tank comprises a one-piece tank, under refrigerating fluidpressure, having: a plurality of parallel finned tubes covered withadsorbent compounds, forming reactors; superposed plates parallel to oneanother and parallel to the tubes at the center of said tank andcomprising both said evaporator and said condensor; at least oneanti-radiation screen disposed between the evaporator-condensor and thereactor tubes; manifolds connecting the reactor tubes and theevaporator-condenser to the inlets and outlets of said circuits.
 2. Animproved thermodynamic apparatus employing adsorption of a refrigeratingfluid on a solid adsorbent, for cooling or heating, comprising:twointerconnected tanks containing a solid compound having a large capacitybut a low energy of adsorption, each tank having:(i) at least onereactor for receiving said adsorbent compound; (ii) at least onecondensor for condensing refrigerating fluid desorbed by the action of ahot fluid passing through adsorbent compound laden with refrigeratingfluid; (iii) at least one evaporator for vaporizing refrigerating fluidadsorbed on the adsorbent compound cooled by a cold circuit; a hotcircuit connectible to the at least one reactor of each of the two tanksfor heating and circulating said hot fluid; an air-conditioning circuitconnectible to the at least one evaporator of each of the two tanks forcooling an enclosure to be air-conditioned; wherein said cold circuit isalternately connectible to the at least one condensor and the at leastone reactor of the two tanks; and wherein each tank comprises aone-piece tank, under refrigerating fluid pressure, having: a pluralityof parallel finned tubes covered with adsorbent compounds, formingreactors; a trickling exchanger at the center of said tank, saidexchanger comprising both said evaporator and said condensors; at leastone anti-radiation screen disposed between the evaporator-condensor andthe reactor tubes; manifolds connecting the reactor tubes and theevaporator-condenser to the inlets and outlets of said circuits.
 3. Theapparatus of claim 1 or 2, wherein the hot circuit has a heat sourceselected from the group consisting of a solar collector and a boiler. 4.The apparatus of claim 2, wherein the cold circuit has a cold sourceselected from the group consisting of an air coolant, a cooling towerconnected to the ambient air, and an available cooling fluid.
 5. Theapparatus of claim 2, wherein the air-conditioning circuit comprises acircuit selected from the group consisting of an air-water battery and aheat exchanger producing ice.
 6. The apparatus of one of claims 1 or 2,wherein said circuits and the two tanks are connected together byconventional pipes and valves under water or thermal oil pressure. 7.The apparatus of claim 1, wherein the solid adsorbent is selected fromthe group including zeolites, activated charcoals, gels of silica andactivated alumina, and the refrigerating fluid is selected from thegroup including water, methanol and ammonia.
 8. A process for operatingthe thermodynamic apparatus of one of claims 1 or 2, comprising thefollowing steps:in a first stage, simultaneously connecting:the hotcircuit to the exchanger to start desorption of the heating fluidthereof, the cold circuit to the reactor of the second tank to allowadsorption of the refrigerating fluid thereon, and simultaneously,removing the heat furnished by the condensation of the refrigeratingfluid on the condensor of the first tank by the cold circuit andremoving from the cooling circuit the energy of vaporization of therefrigerating fluid on the evaporator of the second tank; in a secondstage, connecting together the reactors of the two tanks to thermallyequilibrate these reactors, for cooling the first tank, which thenbegins to adsorb, and to allow pre-heating of the second tank, whichthen begins to desorb, while continuing to remove the heat furnished bythe condensation of the refrigerating fluid on the condensor of thesecond tank on the cold circuit and continuing to remove from thecooling circuit the energy of vaporization of the refrigerating fluid onthe evaporator of the first tank; in a third stage, while continuing toremove the heat furnished by the condensation of the refrigerating fluidon the condensor of the second tank on the cold circuit and to take fromthe cooling circuit the energy of vaporization of the refrigeratingfluid on the evaporator of the first tank, connecting: the hot circuitto the reactor of the second tank for desorption of the latter, the coldcircuit to the reactor of the first tank for adsorption of the latter;in a fourth stage, connecting the reactors of the two tanks again tothermally equilibrate these two reactors again, for the cooling of thesecond tank, which then begins to adsorb, and to allow pre-heating ofthe first tank, which then begins to desorb, while continuing to removethe heat generated by the condensation of the refrigerating fluid on thecondensor of the first tank by the cold circuit and continuing to removefrom the cooling circuit the energy of vaporization of the refrigeratingfluid on the evaporator of the first tank by the cold circuit andcontinuing to remove from the air-conditioning circuit the energy ofvaporization of the refrigerating fluid on the evaporator of the secondtank; and finally, in a fifth stage, connecting:the hot circuit to thereactor of the first tank, the cold circuit to the reactor of the secondtank, and continuing to remove the heat generated by the condensation ofthe refrigerating fluid on the condensor of the first tank by the coldcircuit and continuing to remove from the cooling circuit the energy ofvaporization of the refrigerating fluid on the evaporator of the secondtank.
 9. The process of claim 8, wherein the different connections areregulated by a regulating member which controls opening and closing ofvalves placed in pipes of the different circuits.
 10. The apparatus ofclaims 1 orr 2, wherein each one-piece tank is horizontal andcylindrical, and the finned tubes thereof are disposed around a circleinside the periphery of the tank.